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Scientists Find Possible Window to Martian Life

Researchers from Brown University announce discovery of large deposits of glass formed by impactors on the surface of Mars. Similar impactors on Earth have preserved signatures of ancient life.

Researchers have found deposits of impact glass preserved in Martian craters like Alga (above) using data from NASA’s Compact Reconnaissance Imaging Spectrometer for Mars (CRISM). Image: NASA/JPL-Caltech/JHUAPL/University of Arizona

Using satellite data, the team detected deposits of glass within Martian craters. The glass, which was formed by unimaginable heat brought on by violent impact, could possibly offer a “delicate window into the possibility of past life on the Red Planet.”

Could such a window exist in these unlikely circumstances? Research groups on Earth have shown that terrestrial ancient biosignatures can be preserved in impact glass. In one study, geologists found organic molecules and plant matter in glass that formed during an impact millions of years in the past. Evidence suggests the same process could have occurred on Mars.

Kevin Cannon, a Ph.D. student at Brown and the lead author of the new research, was quoted saying:

The work done by [Brown geologist Peter Schultz] and others showed us that glasses are potentially important for preserving biosignatures. Knowing that, we wanted to go look for them on Mars and that’s what we did here. Before this paper no one had been able to definitively detect them on the surface.

Cannon, along with Jack Mustard, professor of Earth, environmental, and planetary sciences at Brown, has documented large glass deposits in several ancient craters. The presence of glass in these well-preserved impact locations suggests that deposits are common on Mars. Such deposits could be targets for future manned or robotic exploration.

Discovering the glass was no small feat. To do so, the team identified minerals and rock types by measuring the spectra of light reflected off the planet’s surface. Impact glass, however, does not have a very strong spectral signal.

Professor Mustard commented on this fact:

Glasses tend to be spectrally bland or weakly expressive, so signatures from the glass tend to be overwhelmed by the chunks of rock mixed in with it. But Kevin found a way to tease that signal out.

This teasing method involved mixing together “powders with a similar composition of Martian rocks and fired them in an oven to form glass.” This was followed by a measurement of the spectral signal from that glass.

A possible Martian site (white circle) is the Nili Fossae trough. The blue-tinted Hargraves crater at the right is known to contain impact glass. Image: NASA/JPL-Caltech/Arizona State University

Having found the signal from the lab glass, the team designed an algorithm designed “to pick out similar signals in data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), which flies aboard NASA’s Mars Reconnaissance Orbiter.”

The results were a spectacular success. Deposits were found around several crater central peaks. These peaks are the craggy mounds that often form in the center of a crater during a large impact. Finding glass in such a location is a “good indicator that [it has] an impact origin.”

The result of these findings is a new strategy scientists can use to search for ancient Martian life. Success in that regard would rank among the most significant scientific discoveries in human history.

One of the craters found to contain glass is called Hargraves, and it is located near the Nili Fossae trough. The trough is a 400-mile-long depression that stretches across the Martian surface. Even before the discovery of glass, the region was named as a leading contender for the landing site to be used by NASA’s Mars 2020 rover. If selected, the rover will search Nili Fossae for soil and rock samples that may one day be returned to Earth.

Professor Mustard described Nili Fossae’s scientific appeal:

If you had an impact that dug in and sampled that subsurface environment, it’s possible that some of it might be preserved in a glassy component. That makes this a pretty compelling place to go look around, and possibly return a sample.

Scientists are also interested the region because it is thought to date from when Mars was a much wetter place. It is also “rife with what appear to be ancient hydrothermal fractures, warm vents that could have provided energy for life to thrive just beneath the surface.”